Pressure regulating valves are well known in the prior art and are in widespread use in a number of different applications. One such pressure regulating valve is taught, for example, in German Patent No. DE-OS 32 22 247.
The pressure regulating valve taught in this patent has a valve mechanism that is operated by a piston. This valve also has a pressure chamber which is connected to both a pressure entry port and a pressure exit port. Also, this pressure chamber can be connected to the atmosphere by means of a pressure outlet to evacuate pressure from the valve when necessary. This pressure regulating valve serves as a shutoff valve, which is activated by the piston.
Pressure regulating valves, in general, have the disadvantage of generating a considerable amount of noise during the evacuation of pressure from pressure chamber of such valve. Depending upon the proximity of the valve to persons who may be required to be in the area, this noise generated during such pressure evacuation of the valve can be highly undesirable.
A pressure regulating valve, in addition to its shutoff function, has the function of operating as a safety valve. In this case, even with a malfunction of the piston, the valve will move into the open position upon reaching a predetermined pressure level within the pressure chamber.
In general, a pressure regulating valve having this safety function is designed in such a way and dimensioned in such a manner that the diameter of the activating area of the piston positioned in the valve body and which forms a part of the shutoff valve is pressurized by the pressure medium in the pressure chamber and is larger than the diameter of the housing bore which receives the piston.
This construction of the pressure regulating valve makes it possible for the valve mechanism to be moved into the open position even if the activating piston ceases to function. Movement of such pressure regulating valve will occur as long as a predetermined pressure is obtained in the pressure chamber of the valve.
One problem with such a pressure regulating valve is the size requirement for the operating surface of the valve body which is to be subjected to the pressure in such pressure chamber of the valve. For example, when a relatively large valve area has been selected, in order to achieve a guaranteed safety operation of the valve mechanism, the application of a strong closing force, such as exerted by a heavy spring, for the valve will be required. It follows then that, for activating the piston in the opening direction of the valve mechanism, a large force is required, i.e., a high pressure. Therefore, the opening process of such valve mechanism during normal operation, i.e., during operation as a piston-activated shutoff valve, will be delayed. On the other hand, when the operating area of the valve body is relatively small, the safety function of the pressure regulating valve cannot be guaranteed under all operating conditions to which such valve may be subjected during operation.